diff: check syntax of `some' goals

[Fergus Henderson]

Estimated hours taken: 0.5

Report an error if the first argument of a `some' goal
is not a list of variables.

compiler/prog_io.m:
compiler/prog_io_util.m:
	Move `parse_list_of_vars' from prog_io.m to prog_io_util.m.

compiler/prog_io_goal.m:
	Check to make sure that the first argument to a some
	goal is a list of variables.  (If not, we don't report
	an error here -- the error will be reported by typecheck.m.)

compiler/typecheck.m:
	Report an proper error message if there is a call to an
	undefined predicate `some/2'.
	Also add `some/2' and `all/2' to the list of language builtins
	for which we report a special error message if they occur as
	undefined function symbols.

Index: compiler/prog_io.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/prog_io.m,v
retrieving revision 1.176
diff -u -r1.176 prog_io.m
--- prog_io.m	1998/10/29 08:53:06	1.176
+++ prog_io.m	1998/10/29 14:23:27
@@ -1044,14 +1044,6 @@
 		quantifier(univ, TVarsList), Decl) :-
 	parse_list_of_vars(TVars, TVarsList).
 
-:- pred parse_list_of_vars(term, list(var)).
-:- mode parse_list_of_vars(in, out) is semidet.
-	
-parse_list_of_vars(term__functor(term__atom("[]"), [], _), []).
-parse_list_of_vars(term__functor(term__atom("."), [Head, Tail], _), [V|Vs]) :-
-	Head = term__variable(V),
-	parse_list_of_vars(Tail, Vs).
-
 :- pred check_no_attributes(maybe1(item), decl_attrs, maybe1(item)).
 :- mode check_no_attributes(in, in, out) is det.
 
Index: compiler/prog_io_goal.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/prog_io_goal.m,v
retrieving revision 1.12
diff -u -r1.12 prog_io_goal.m
--- prog_io_goal.m	1998/06/09 02:14:28	1.12
+++ prog_io_goal.m	1998/10/29 14:35:58
@@ -193,7 +193,7 @@
 	parse_goal(B0, V1, B, V).
 
 parse_goal_2("some", [Vars0, A0], V0, some(Vars, A), V):-
-	term__vars(Vars0, Vars),
+	parse_list_of_vars(Vars0, Vars),
 	parse_goal(A0, V0, A, V).
 
 	% The following is a temporary hack to handle `is' in
@@ -227,9 +227,10 @@
 
 parse_some_vars_goal(A0, VarSet0, Vars, A, VarSet) :-
 	( 
-		A0 = term__functor(term__atom("some"), [Vars0, A1], _Context)
+		A0 = term__functor(term__atom("some"), [Vars0, A1], _Context),
+		parse_list_of_vars(Vars0, Vars1)
 	->
-		term__vars(Vars0, Vars),
+		Vars = Vars1,
 		parse_goal(A1, VarSet0, A, VarSet)
 	;
 		Vars = [],
Index: compiler/prog_io_util.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/prog_io_util.m,v
retrieving revision 1.10
diff -u -r1.10 prog_io_util.m
--- prog_io_util.m	1998/03/27 18:52:33	1.10
+++ prog_io_util.m	1998/10/29 14:25:33
@@ -42,6 +42,14 @@
 :- pred add_context(maybe1(item), term__context, maybe_item_and_context).
 :- mode add_context(in, in, out) is det.
 
+%
+% Various predicates to parse small bits of syntax.
+% These predicates simply fail if they encounter a syntax error.
+%
+
+:- pred parse_list_of_vars(term, list(var)).
+:- mode parse_list_of_vars(in, out) is semidet.
+
 :- pred convert_mode_list(list(term), list(mode)).
 :- mode convert_mode_list(in, out) is semidet.
 
@@ -51,9 +59,6 @@
 :- pred convert_inst_list(list(term), list(inst)).
 :- mode convert_inst_list(in, out) is semidet.
 
-	% Parse an inst.
-	% Fails on syntax errors.
-	%
 :- pred convert_inst(term, inst).
 :- mode convert_inst(in, out) is semidet.
 
@@ -101,6 +106,11 @@
 
 add_context(error(M, T), _, error(M, T)).
 add_context(ok(Item), Context, ok(Item, Context)).
+
+parse_list_of_vars(term__functor(term__atom("[]"), [], _), []).
+parse_list_of_vars(term__functor(term__atom("."), [Head, Tail], _), [V|Vs]) :-
+	Head = term__variable(V),
+	parse_list_of_vars(Tail, Vs).
 
 convert_mode_list([], []).
 convert_mode_list([H0|T0], [H|T]) :-
Index: compiler/typecheck.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/typecheck.m,v
retrieving revision 1.254
diff -u -r1.254 typecheck.m
--- typecheck.m	1998/10/29 09:20:00	1.254
+++ typecheck.m	1998/10/29 14:34:02
@@ -4706,6 +4706,14 @@
 			[]
 		)
 	;
+		{ PredName = unqualified("some"), Arity = 2 }
+	->
+		io__write_string(
+		    "  syntax error in existential quantification: first\n"),
+		prog_out__write_context(Context),
+		io__write_string(
+		    "  argument of `some' should be a list of variables.\n")
+	;
 		io__write_string("  error: undefined predicate `"),
 		hlds_out__write_pred_call_id(PredCallId),
 		io__write_string("'"),
@@ -4977,6 +4985,8 @@
 language_builtin("call", _).
 language_builtin("impure", 1).
 language_builtin("semipure", 1).
+language_builtin("all", 2).
+language_builtin("some", 2).
 
 :- pred write_call_context(term__context, pred_call_id, int, unify_context,
 				io__state, io__state).

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>  |  of excellence is a lethal habit"
PGP: finger fjh at 128.250.37.3        |     -- the last words of T. S. Garp.